CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Main CFD Forum

artifcats in an radialy expending flow

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   December 5, 2003, 13:33
Default artifcats in an radialy expending flow
  #1
Mehdi
Guest
 
Posts: n/a
Hi,

I am trying to model the 2D shock between two compressible hypersonic flows. one of my two flows is expending radialy form a source placed in the middle of my space domain. I am using an Upwind-Lax-Friedrich scheme to resolve my Euler's equations, with an cartesian structured grid.

I have a problem in modeling the radial expansion of my first flow. The circular source is discretised using 32*32 cells. When my flow start to radially expend from the source, artifacts occurs showing anomalies between the grid aligned direction and the diagonal directions.

I saw that the major part of works done on that subject (expanding flow or detonation) use curviliniar mesh more appropriate to treat radial expansion.

Infortunatly I need to use my cartesian grid. Is there any solution to minimize the effect of these artifacts (other than using an extreme level of refinement near the source).

Thank you in advance

Mehdi
  Reply With Quote

Old   December 9, 2003, 02:07
Default Re: artifcats in an radialy expending flow
  #2
versi
Guest
 
Posts: n/a
Upwind-Lax-Friedrich (1st order) is very dissipative, can not be reliable. You can choose other 2nd scheme, like MUSCL-Roe, TVD, ENO. Gundnov. Also there is a problem of boundary well posedness for source flow.
  Reply With Quote

Old   December 9, 2003, 11:23
Default Re: artifcats in an radialy expending flow
  #3
Praveen
Guest
 
Posts: n/a
I am assuming you are using a finite volume method. In that case are you taking cell-averages for initial condition ? The cell-average contains more information about initial discontinuity and is absolutely essential to get correct solution.
  Reply With Quote

Old   December 10, 2003, 12:23
Default Re: artifcats in an radialy expending flow
  #4
Mehdi
Guest
 
Posts: n/a
Hi,

Thank you for you advance, I am just identifing the problem : I am using for my reconstruction a limiter based on albada formula. In this limiter I use only the four surrounding neighbors (I am in 2-D) to compute the forward and the backward diffrence operator and to extrapolate form there to the the face values.

I tried a Minmod limiter that include the corner cells amd it working pretty good. My artifacts completly disapeared for the diagonal moving flow.

The Question That rise now is how to take account of the corner cells in the classic interpollation scheme using the forward and the backward difference ?

Mehdi
  Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
benchmark: flow over a circular cylinder goodegg Main CFD Forum 12 January 22, 2013 12:47
Mass flow and U-Mom flow in CFX Zhihua Xie CFX 0 September 3, 2007 09:49
reversed flow at velocity inlet / mass flow inlet ib FLUENT 1 March 26, 2007 13:11
How to change from mass flow to volume flow rate stanley FLUENT 1 February 2, 2007 07:44
transform navier-stokes eq. to euler-eq. pxyz Main CFD Forum 37 July 7, 2006 08:42


All times are GMT -4. The time now is 09:10.